Controllers must issue pertinent information on observed/reported weather and chaff areas to potentially affected
aircraft. Define the area of coverage in terms of:
Azimuth (by referring to the 12-hour clock) and distance from the aircraft and/or
The general width of the area and the area of coverage in terms of fixes or distance and direction from fixes.
NOTE: Weather significant to the safety of aircraft includes conditions such as funnel cloud activity, lines of
thunderstorms, embedded thunderstorms, large hail, wind shear, microbursts, moderate to extreme turbulence
(including CAT), and light to severe icing.
WEATHER/CHAFF AREA BETWEEN (number) O'CLOCK AND (number) O'CLOCK (number) MILES,
(number) MILE BAND OF WEATHER/CHAFF FROM (fix or number of miles and direction from fix) TO (fix or number of
miles and direction from fix).
Inform any tower for which you provide approach control services of observed precipitation on radar which is
likely to affect their operations.
Use the term “precipitation” when describing radar-derived weather. Issue the precipitation intensity from the
lowest descriptor (LIGHT) to the highest descriptor (EXTREME) when that information is available. Do not use the
word “turbulence” in describing radar-derived weather.
NOTE: Weather and Radar Processor (WARP) does not display light intensity.
AREA OF (Intensity) PRECIPITATION BETWEEN (number) O'CLOCK AND (number) O'CLOCK, (number) MILES, MOVING
(direction) AT (number) KNOTS, TOPS (altitude). AREA IS (number) MILES IN DIAMETER.
1. “Area of heavy precipitation between ten o'clock and two o'clock, one five miles. Area is two five miles in
2. “Area of heavy to extreme precipitation between ten o'clock and two o'clock, one five miles. Area is two
five miles in diameter.”
TERMINAL. In STARS, correlate precipitation descriptors from subparagraph c as
Level 1 = LIGHT
Level 2 = MODERATE
Level 3 and 4 = HEAVY
Level 5 and 6 = EXTREME
When precipitation intensity information is not available.
AREA OF PRECIPITATION BETWEEN (number) O' CLOCK AND (number) O' CLOCK, (number) MILES. MOVING (direction) AT
(number) KNOTS, TOPS (altitude). AREA IS (number) MILES IN DIAMETER, INTENSITY UNKNOWN.
“Area of precipitation between one o'clock and three o'clock, three five miles moving south at one five knots,
tops flight level three three zero. Area is three zero miles in diameter, intensity unknown.”
NOTE: Phraseology using precipitation intensity descriptions is only applicable when the radar precipitation
intensity information is determined by NWS radar equipment or NAS ground based digitized radar equipment with
weather capabilities. This precipitation may not reach the surface.
EN ROUTE. When issuing Air Route Surveillance Radar (ARSR) precipitation
intensity use the following:
Describe the lowest displayable precipitation intensity as MODERATE.
Describe the highest displayable precipitation intensity as HEAVY to EXTREME.
AREA OF (Intensity) PRECIPITATION BETWEEN (number) O'CLOCK and (number) O'CLOCK, (number) MILES, MOVING
(direction) AT (number) KNOTS, TOPS (altitude). AREA IS (number) MILES IN DIAMETER.
1. “Area of moderate precipitation between ten o'clock and one o'clock, three zero miles moving east at two
zero knots, tops flight level three seven zero."
2. “Area of moderate precipitation between ten o'clock and three o'clock, two zero miles. Area is two five
miles in diameter.”
Controllers must ensure that the highest available level of precipitation intensity within their area of
jurisdiction is displayed unless operational/equipment limitations exist.
When requested by the pilot, provide radar navigational guidance and/or approve deviations around weather or chaff
areas. In areas of significant weather, plan ahead and be prepared to suggest, upon pilot request, the use of
An approval for lateral deviation authorizes the pilot to maneuver left or right within the lateral limits
specified in the clearance.
When approving a weather deviation for an aircraft that had previously been issued a crossing altitude,
including climb via or descend via clearances, issue an altitude to maintain and, if necessary, assign a speed
along with the clearance to deviate. If you intend on clearing the aircraft to resume the procedure, advise
DEVIATION (restrictions, if necessary) APPROVED, MAINTAIN (altitude), (if necessary) MAINTAIN (speed), (if
applicable) EXPECT TO RESUME (SID/STAR, etc.) AT (NAVAID, fix/waypoint).
NOTE: After a climb via or descend via clearance has been issued, a vector/deviation off of a SID/STAR
cancels all published altitude and speed restrictions on the procedure. The aircraft's Flight Management
System (FMS) may be unable to process crossing altitude restrictions once the aircraft leaves the SID/STAR
lateral path. Without an assigned altitude, the aircraft's FMS may revert to leveling off at the altitude
set by the pilot, which may be the SID/STAR published top or bottom altitude.
If a pilot enters your area of jurisdiction already deviating for weather, advise the pilot of any additional
weather which may affect the route.
NOTE: When aircraft are deviating around weather and transitioning from sector to sector, unless previously
coordinated, the receiving controller should not assume that the transferring controller has issued weather
affecting the aircraft's route of flight.
If traffic and airspace (i.e., special use airspace boundaries, LOA constraints) permit, combine the approval
for weather deviation with a clearance on course.
DEVIATION (restrictions if necessary) APPROVED, WHEN ABLE, PROCEED DIRECT (name of NAVAID/WAYPOINT/FIX)
DEVIATION (restrictions if necessary) APPROVED, WHEN ABLE, FLY HEADING (degrees), VECTOR TO JOIN (airway)
1. “Deviation 20 degrees right approved, when able proceed direct O'Neill VORTAC and advise.” En Route:
The corresponding fourth line entry is “D20R/ONL” or “D20R/F.”
2. “Deviation 30 degrees left approved, when able fly heading zero niner zero, vector to join J324 and
advise.” En Route: In this case the free text character limitation prevents use of fourth line
coordination and verbal coordination is required.
If traffic or airspace prevents you from clearing the aircraft on course at the time of the approval for a
weather deviation, instruct the pilot to advise when clear of weather.
DEVIATION (restrictions if necessary) APPROVED, ADVISE CLEAR OF WEATHER.
“Deviation North of course approved, advise clear of weather.”
En Route: In this case the corresponding fourth line entry is “DN,” and the receiving controller must
provide a clearance to rejoin the route in accordance with paragraph 2-1-15 c.
When a deviation cannot be approved as requested because of traffic, take an alternate course of action that
provides positive control for traffic resolution and satisfies the pilot's need to avoid weather.
UNABLE REQUESTED DEVIATION, FLY HEADING (heading), ADVISE CLEAR OF WEATHER.
UNABLE REQUESTED DEVIATION, TURN (number of degrees) DEGREES (left or right) VECTOR FOR TRAFFIC, ADVISE CLEAR
“Unable requested deviation, turn thirty degrees right vector for traffic, advise clear of weather.”
When forwarding weather deviation information, the transferring controller must clearly coordinate the nature of
the route guidance service being provided. This coordination should include, but is not limited to: assigned
headings, suggested headings, pilot-initiated deviations. Coordination can be accomplished by: verbal, automated,
or predetermined procedures. Emphasis should be made between: controller assigned headings, suggested headings, or
pilot initiated deviations.
“(call sign) assigned heading three three zero for weather avoidance”
The inclusion of a NAVAID, waypoint, or /F in the fourth line data indicates that the pilot has been
authorized to deviate for weather and must rejoin the route at the next NAVAID or waypoint in the route of
“Deviation twenty degrees right approved, when able proceed direct O'Neill VORTAC and advise.” In this
case, the corresponding fourth line entry is “D20R/ONL” or “D20R/F.”
The absence of a NAVAID, waypoint, or /F in the fourth line indicates that:
(a) The pilot has been authorized to deviate for weather only, and the receiving controller must provide a
clearance to rejoin the route in accordance with paragraph 2-1-15c.
“Deviation twenty degrees right approved, advise clear of weather.”
(b) The free text character limitation prevents the use of fourth line coordination. Verbal coordination
“Deviation 30 degrees left approved, when able fly heading zero niner zero, vector to join J324 and
The supervisory traffic management coordinator-in-charge/operations supervisor/controller-in-charge must verify
the digitized radar weather information by the best means available (e.g., pilot reports, local tower personnel,
etc.) if the weather data displayed by digitized radar is reported as questionable or erroneous. Errors in weather
radar presentation must be reported to the technical operations technician and the air traffic supervisor must
determine if the digitized radar derived weather data is to be displayed and a NOTAM distributed.
NOTE: Anomalous propagation (AP) is a natural occurrence affecting radar and does not in itself constitute a
weather circuit failure.